Each year, as the dry season comes to a close, Maui Nui hosts a number of returning seasonal visitors. No, we’re not talking about the flock of human “snowbirds” coming from the east, but rather the animals that have been heading this way for millenia: kōlea (Pacific golden plovers), koholā (humpback whales), and niuhi (tiger sharks).
The kōlea have done all their breeding, birthing, and family raising far away in Alaska and are back for some rest in the sunny weather. The koholā are coming to give birth and breed. While the koholā won’t feed until they return to Alaska in the spring (tropical waters just don’t have abundant whale food), the waters around Hawai‘i are a great place for the baby whales to take off their training wheels. For our tiger sharks, the waters around Maui provide ample feeding opportunities for the new and repeat shark moms to recharge after pregnancy.
The tiger shark birthing season starts in October and correlates with increased reports of shark incidents. The kānaka maoli were well aware of this. The expression, “Pua ka wiliwili, nanahu ka manō” (“When the wiliwili tree blooms, sharks will bite”) is one example of traditional ecological knowledge about sharks (manō) passed down through generations in Hawaiian chants and stories.
Maui, in particular, holds the dubious record of having almost double the number of shark incidents reported on other islands, and there is a tiny but significant uptick in incidents during what some have dubbed “Sharktober.”
But why Maui Nui and why Maui in particular? This is a question that researchers from the Hawaiʻi Institute of Marine Biology have been studying for a number of years with telemetry programs. The program, started by Kim Holland and his graduate students in the mid-’90s to measure the effectiveness of shark “culling” activities (conducted from 1959-’76 on Oahu), intended to reduce tiger shark populations to “safer” levels. Despite catching over 4,500 sharks, the program did not appear to have any effect on the number of shark incidents during that time.
Culling would only work if sharks were living in the same area and remaining close to shore. Initial tagging efforts showed that tiger sharks tagged off of Oahu did not hang around, but rather were passing through and quickly left for Penguin Bank, miles east of Oahu and just west of Molokai. As a result, shark culling was decided not to be an effective management tool and has not been reinstated in Hawai‘i since.
At the start of the shark-tracking program, HIMB researchers had to first catch a shark and surgically implant an acoustic tracker or “pinger” that the scientists would then actively monitor for up to two days. A follow-up project equipped sharks with transmitters that would get picked up by listening stations anchored around the main Hawaiian islands. When the tagged shark swam within about half a mile of a receiver, its visit was recorded. This work again showed that tiger sharks moved around a lot and it was not uncommon for individuals to swim between islands.
In 2013 and 2014, the HIMB team attached new satellite-connected trackers to tiger sharks’ dorsal fins. These allowed them to follow the movements of sharks tagged around Maui and Oahu for months or even years and with finer resolution. They also used the tried and true acoustic tags and listening stations deployed along the coastline. The results of this last study were published in a scientific paper and provided several clues to the observed patterns of shark incidents in Hawai’i.
While sharks tend to range widely and spend quite a bit of time far offshore in deeper water, they frequent shallow coastal areas. Overall, the prime habitat for the tagged sharks was the “insular shelf” down to a depth of 200 meters (656 ft.) and Maui Nui has the most extensive insular shelf area in Hawai’i. Sharks tagged on Maui ranged around quite a bit but still had “core areas” they would be most frequently found. While some sharks had offshore core areas (for example at Penguin Bank) researchers discovered several sharks’ core areas clustered along the south Maui coastline from Kihei to Makena. In contrast to Maui, Oahu sharks’ core areas had less overlap with recreational areas.
The acoustic receivers also picked up sharks as they passed by receiver stations and discovered that, effectively, tiger sharks are checking in at some of the more popular beaches on Maui. While they don’t appear to be hanging out at these areas, acoustic receivers showed that sharks were swimming by about every other day along Makena and Kalama and about once every four days at Palauea and Olowalu.
So it seems that Maui has more areas where people are getting in the water along with tiger sharks and, come October, at least some of those sharks may be extra grumpy or hungry after giving birth. Even so, it is important to remember: even with sharks present and possibly common along our beaches, sharks are not trying to harm people. In truth, count yourself lucky if you ever even get to see one of Maui’s tiger sharks. Shark incidents are truly one in a million events. You are at greater risk of injury from many other things: a firearm, alcohol and a car, someone’s pet dog, or even a slip in the shower.
If you want to reduce your odds of meeting sharks, there are several things you can do, including staying out of water with poor visibility, not swimming alone, and not swimming close to people that are line, net or spear fishing. See the DLNR Shark Safety Tips link for more recommendations.
Hawai’i Tiger Shark Track Viewer – https://www.pacioos.hawaii.edu/projects/sharks/
Hawai’i Tiger Shart Track Project Report – https://www.nature.com/articles/s41598-018-23006-0.epdf
DLNR Hawai’i Sharks Website – https://dlnr.hawaii.gov/sharks/
DLNR Shark Safety Tips – https://dlnr.hawaii.gov/sharks/shark-safety/safety-tips/
Understanding Sharks in Hawaiian Culture – https://core.ac.uk/download/pdf/343749231.pdf